Valley’s weeds test the skills of young scientist

THE bad guys come at us from every direction: needlegrass from Chile, boxthorn from Africa, broom and gorse from England, karumu from New Zealand and orange hawkweed from Europe. And then there’s blackberry.

To call them invasive species is just the beginning. Beyond the sheer number of these weed pests, the habitat they occupy varies from steep slopes to marshland, rocky mountain soils to prime orcharding land. There is also conflict: their autumn colours add to the natural beauty of this place while the plants choke waterways, impacts native habitat and reduce productivity on farms. Simple grazing can be effective in keeping weeds in check, but a short distance away, intervention in the form of regular spraying or ‘cut and paste’ with herbicide will be required to manage incursions. And sometimes, brute force in the form of a chainsaw or brushcutter is the only way.

Weed management is a complicated business and seriously tests the skills of even a smart young scientist like Morgan McPherson. Mr McPherson is the Operations Manager for the Derwent Catchment Project, a local not-for-profit land and water management organisation. He has recently completed his master’s degree in integrated water management through Griffith University. He brings a focused lens to the health of the landscape across the Derwent Valley.

Five years ago, the Derwent Catchment Project wrote a strategic plan to best tackle invasive weeds. The core task was mapping: working out what weeds were growing where. The plan identified high priority zones, such as high conservation value and prime agricultural areas. As there are limited resources for weed management these key ‘weed eradication zones’ set the priority areas for the on-ground team to undertake weed control. “One of the limitations is the small rate base across the Valley,” says Morgan.

“There are only so many resources for weed management in a regional area with extensive road networks.” The funding question has been answered, at least in part, by community engagement involving public and private sectors, from orchardists to power generators, foresters and fishermen – everybody with a stake – often, but not necessarily financial, in managing the hydraheaded weed issue. A core concern is the impacts on agricultural sectors, such as cherry-growing, presented by bio-security threats. Via a farm visit or hotel stay, a visitor could all too easily bring into the Valley a new or known pest.

A real concern is the fruit fly, long deeply problematic for a state that prides itself on its fruit exports. “While our colder winters have kept the fruit fly out of here so far the likelihood is that climate change will alter that delicate balance,” says Mr McPherson, “The long-term issue with blackberries, for instance, is their extensive distribution along many of our roads, fencelines and watercourses like the Derwent. “Those form a kind of a highway for fruit fly to move into high value crops like cherries.”

Mr McPherson doesn’t need to spell out the impact such a change could have on a stonefruit sector worth $50 million a year to our economy. “We’ve been lucky with fruit fly so far, catching it in on supermarket shelves in Tasmania. Can that luck hold?” he asks. “I understand the blackberry issue, indeed the whole ‘foraging for food’ idea. Blackberry picking along the Derwent has deep roots as a pastime. “But we’re not talking about getting rid of all blackberries, just controlling the areas that pose a biosecurity threat or impact on natural values. “Blackberries impact a whole range of other human activities, including swimming, kayaking and hiking, but they also make it difficult to manage other weed issues such as willows.”

Mr McPherson says a managed program to spray blacberries in selected locations begins in November this year. “But not once there’s fruit on the plants. “There’s a limited window of opportunity to knock them down,” he says. “And even if we keep this up for three or four years, there will still be plenty of them around the Derwent Valley for picking by all the blackberry pie fanciers out there. “At least we’ll know where they are!”